A non-contact power receiving circuit is known in the related art that includes a power receiving part coupled to a proximity magnetic field of the non-contact power receiving circuit, a rectifying part that rectifies an output voltage of the power receiving part, a DC-DC converter that transforms the output voltage of the rectifying part to output the transformed voltage to a power receiving load, and a load modulating part that changes an impedance of the entire circuit by performing load modulation in signal transmission to the non-contact power receiving circuit.
The non-contact power receiving circuit further includes an impedance variable part and a first capacity part connected between the rectifying part and the DC-DC converter via the impedance variable part. The impedance variable part becomes a high impedance in the signal transmission and becomes a low impedance in power transmission. The non-contact power receiving circuit further includes a smoothing capacity part that smooths an output voltage from the rectifying part (for example, see Patent Document 1).
In the non-contact power receiving circuit in the related art, the following problem may occur when a secondary battery such as a battery is connected to an output side of the DC-DC converter to charge the secondary battery.
In a case where the secondary battery has a safety device so as not to draw current until a voltage stabilizes when starting to charge the secondary battery, it is impossible to supply the current from the DC-DC converter to the secondary battery in a time period until the voltage becomes stable.
The time period until the voltage becomes stable is about one or several seconds, for example.
When it becomes impossible to supply the current to the secondary battery from the DC-DC converter, the safety device of the DC-DC converter operates to stop the operation of the DC-DC converter.
As a result, in the non-contact power receiving circuit in the related art, it may be impossible to stably charge the secondary battery as described above.